contentprovider读写代码

以下是一个简单的 ContentProvider 读写代码示例：

public class MyContentProvider extends ContentProvider {

    private static final String AUTHORITY = "com.example.mycontentprovider";
    private static final String TABLE_NAME = "mytable";
    private static final int URI_CODE = 1;
    private static final UriMatcher URI_MATCHER = new UriMatcher(UriMatcher.NO_MATCH);

    static {
        URI_MATCHER.addURI(AUTHORITY, TABLE_NAME, URI_CODE);
    }

    private SQLiteDatabase database;

    @Override
    public boolean onCreate() {
        database = new MyDatabaseHelper(getContext()).getWritableDatabase();
        return true;
    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
        Cursor cursor = null;
        switch (URI_MATCHER.match(uri)) {
            case URI_CODE:
                cursor = database.query(TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder);
                break;
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        return cursor;
    }

    @Nullable
    @Override
    public String getType(@NonNull Uri uri) {
        return null;
    }

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
        Uri resultUri = null;
        switch (URI_MATCHER.match(uri)) {
            case URI_CODE:
                long id = database.insert(TABLE_NAME, null, values);
                resultUri = ContentUris.withAppendedId(uri, id);
                break;
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        return resultUri;
    }

    @Override
    public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
        int count = 0;
        switch (URI_MATCHER.match(uri)) {
            case URI_CODE:
                count = database.delete(TABLE_NAME, selection, selectionArgs);
                break;
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        return count;
    }

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
        int count = 0;
        switch (URI_MATCHER.match(uri)) {
            case URI_CODE:
                count = database.update(TABLE_NAME, values, selection, selectionArgs);
                break;
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        return count;
    }
}

这是一个简单的 ContentProvider 实现，它可以对一个名为 "mytable" 的表进行读写操作。在 onCreate() 方法中，我们获取了一个可写的 SQLiteDatabase 对象，这个对象可以用于执行 SQL 语句。在 query()、insert()、delete()、update() 方法中，我们根据传入的 Uri 参数来判断要操作的表以及要执行的操作类型，然后调用 SQLiteDatabase 对象的相应方法来执行操作。